This invention relates to a machine having a working arm and more particularly but not exclusively to a machine known as an articulated shovel which has a first body part connected to a second body part of the machine by an articulated connection which permits of relative movement between the first and second body parts of the machine about a generally upright axis. Usually an engine or other power means for the machine, together with an operator""s cab are provided on the second body part, and the first body part mounts the working arm which carries at an end thereof remote from the first body part, a bucket or other working implement.
Conventionally articulated loading shovels have had a pair of spaced apart working arms, which are both mounted at first ends thereof on the first body part, and carry between them at their second ends, the bucket or other working implement. A pair of working arms have been provided primarily in order to provide the necessary strength as the arm lifts heavy loads. Thus each arm has usually been provided with its own lifting actuator.
Articulated loading shovels with single working arms of general box configurations have been proposed, for example in GB patent application 2333759. Such box configuration single working arms have advantages over providing a pair of working arms in that the single working arm can be made lighter than comparable twin arm arrangements, thereby improving the lifting performance of the working arm. However a single arm construction can present an obstacle to an operator""s sight line and accordingly, in arrangements such as in GB patent application 2333759 such single arms have had complex geometrical configurations such that they are by no means straight. Manufacturing working arms with such complex geometrical configurations adds cost to an otherwise economical construction because the complex configuration arm needs to be fabricated from a plurality of components. Moreover, in the arrangement of GB patent application 2333759, the strength of the working arm is compromised by several cut-outs required for providing a pivotal connection between the arm and the machine, and for tilt links which extend through a slot in the arm and are used in the control and operation of the working implement.
According to one aspect of the present invention we provide a machine having a working arm, the machine including a body part to which a first end of the arm is attached for relative pivotal movement about a first generally horizontal axis and the arm having a second end adapted to mount a working implement for movement relative to the arm about a second generally horizontal axis characterised in that the arm is substantially straight between the first and second ends, and is of substantially inverted channel configuration having a top part and a pair of side walls integrally formed, and the arm over at least a major portion of its length between the first and second ends including a strengthening member which extends between and is connected to the side walls.
By virtue of this geometrically simple construction, the working arm may be made very economically. To avoid compromising the strength of the arm where the arm is connected to the machine, the body part of the machine may include a pair of mounting members between which the first end of the arm is received, there being a first pivot means which extends between the mounting members and through the side walls of the arm pivotally to attach the arm to the body part. Of course it may be required to strengthen the side walls locally where the first pivot means passes through, but there is no need to provide any slots or the like in the arm to provide a connection to the body part.
Moreover, to ensure that the arm is as strong as possible in the region of connection to the body part, the strengthening member of the arm may extend between the first pivot means and free edges of the side walls of the arm, and if desired the strengthening member of the arm may at least substantially close the channel of the arm at the first end of the arm, and may be connected to the top part of the arm.
Because the strengthening member is a separate component to the integrally formed top part and side walls, and may for example be plate-like, the strengthening member may be formed to a complex configuration prior to its connection e.g. by welding, to and between the side walls.
Whereas a pair of lifting actuators may be provided if desired, preferably the machine includes a single linearly acting lifting actuator which extends between and is pivotally connected to the body part and to the arm, the lifting actuator when extended and retracted causing movement of the arm relative to the body part about the first generally horizontal axis.
The lifting actuator is preferably connected to the arm by a second pivot means, which may include a pivot pin, which is received by the side walls of the arm, with either bearings between the actuator and pin or between the pin and arm, and the strengthening member may be configured to extend between the second pivot means and the top part of the arm. In this way the strengthening member can be configured to present no obstacle to the operation of the lifting actuator.
Preferably though, the strengthening member of the arm, over a major portion of its length, is connected between the side walls adjacent free edges of the side walls. The side walls of the arm may vary in depth along the arm, and may extend for a maximum distance from the top part in the region of connection of the lifting actuator to the arm where maximum strength is required.
To enable the working implement to be moved about the second generally horizontal axis, there may be provided a pair of tilt links, one link of the pair being pivotally attached at each side of the arm to a respective side wall of the arm, the tilt links further each having a first end positioned above the top part of the arm, and a second end positioned below the arm, the first ends of the tilt links being pivotally connected to a linearly acting tilting actuator which extends generally along the arm and is mechanically connected to the working implement at the second end of the arm, and the second ends of the tilt links being pivotally connected to link means which are pivotally connected to the body part of the machine, the tilting actuator when extended and retracted causing movement of the working implement about the second generally horizontal axis.
Thus again no slot or the like is required to accommodate the tilt links. Furthermore, with an appropriate geometry of tilt links, tilting actuator and link means, the working implement can be arranged automatically to maintain an orientation relative to the ground as the working arm is lifted and lowered by the lifting actuator, without the need to extend or retract the tilting actuator.
In one arrangement the tilting actuator is mechanically connected to the working implement at the second end of the arm by a coupling means which includes a coupling member which is pivotally connected at a first pivot connection to the tilting actuator and at a second pivot connection to the working implement, there being a guide means pivotally connected to the coupling member and to the arm, which guide means may include at least one guide member pivotally connected at one end to the coupling member between the first and second pivot connections, and the guide member being pivotally connected at an opposite end to a side wall of the arm.
Although the invention may be applied to any machine having a working arm, the invention has been particularly developed for use where the body part of the machine to which the working arm is attached is a first body part of the machine which is connected to a second body part of the machine by an articulated connection which permits of relative movement between the first and second body parts of the machine about a generally upright axis. The first and second body parts may be relatively articulated about the generally upright axis by linear actuators, and the first and second body parts of the machine may each include a pair of ground engaging wheels, with at least one of the pairs of wheels being driven from a power means, such as an engine, mounted in or on the second body part of the machine via a mechanical and/or hydrostatic transmission.
An operator""s cab may be provided on the second body part of the machine, positioned between the power means and the first body part of the machine.
According to a second aspect of the invention we provide a working arm for a machine, the arm having a first end adapted to be attached relative to a body part of the machine for relative pivotal movement about a first generally horizontal axis and a second remote end, adapted to mount a working implement for movement relative to the arm about a second generally horizontal axis, characterised in that the arm is substantially straight between the first and second ends, and is of substantially inverted channel configuration having a top part and a pair of side walls integrally formed by pressing from a blank, and the arm over at least a major portion of its length between the first and second ends including a strengthening member which extends between and is connected to the side walls.
The arm may have any of the features of the arm for the machine of the first aspect of the invention. Particularly the side walls of the arm may vary in depth from the top part, which configuration may be achieved by forming a suitably configured blank to the channel shape of the arm.
For example, the depths of the side walls from the top part may be at a maximum depth at a region of the arm which is adapted to be pivotally connected to a lifting actuator where greatest strength is required.
According to a third aspect of the invention we provide a working arm for a machine, the arm having a first end adapted to be attached relative to a body part of the machine for relative pivotal movement about a first generally horizontal axis and a second remote end, adapted to mount a working implement for movement relative to the arm about a second generally horizontal axis, characterised in that the arm is substantially straight between the first and second ends and the arm includes a tilt mechanism including a pair of tilt links, one link of the pair being pivotally attached at each side of the arm to a respective side wall of the arm, the tilt links further each having a first end positioned above the arm, and a second end positioned below the arm, the first ends of the tilt links being pivotally connected to a linearly acting tilting actuator which extends generally along the arm and is in use, mechanically connected to the working implement at the second end of the arm, and the second ends of the tilt links being pivotally connected to link means which are pivotally connected in use to a body part of the machine.
According to a fourth aspect of the invention we provide a method of making a working arm according to the second or third aspects of the invention including the steps of cutting from a sheet of material, a blank, forming the blank into a substantially straight channel shape having a top part and a pair of side walls, and thereafter, over at least a major portion of the length of the channel connecting a strengthening member to each of the side walls so as to extend therebetween.